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Fish Oil Failed to Protect Older People from Alzheimer’s Disease

Observational studies have suggested that omega-3 fats can help protect the brain, but in this trial fish oil failed to improve tests of cognitive function.

Previous studies have suggested that people who eat diets rich in omega-3 fats from fish or nuts are more likely to retain their cognitive abilities. But now a randomized controlled trial shows that fish oil supplements won’t do the job for older Americans.

Taking Advantage of AREDS2:

Cognitive testing was included as part of a trial (the Age-Related Eye Disease Study 2) that was primarily designed to see whether fish oil, together with other supplemental nutrients, could slow the development of macular degeneration, a common eye condition that may cause blindness among older people. The volunteers were tested for cognitive ability at the start of the study and every two years after that.

This part of the AREDS2 trial included more than 3,500 older people (average age 73) who were randomly assigned to one gram of fish oil or placebo supplements daily. The study lasted nearly six years. None of the participants had been diagnosed with dementia prior to the start of the study.

Supplements with Fish Oil Failed to Boost Scores on Cognitive Tests:

Cognitive changes during that time did not differ between the groups, whether they were taking fish oil or placebo, or the other compounds being tested against macular degeneration, lutein + zeaxanthin or placebo.

Although the basic supplements in the AREDS2 study did help keep moderate macular degeneration from getting worse, as we wrote here, neither the lutein/zeaxanthin nor the fish oil was helpful against this devastating eye disease either. Although it probably makes sense to include fish in the diet, we don’t know of randomized trials that would determine that conclusively.

JAMA, Aug. 25, 2015

An editorial in the same issue notes that the best evidence at reducing the risk of dementia is for people not smoking, exercising regularly and getting more education in their younger years. It is sad that the study on exercise published in the same issue of the JAMA did not show any significant benefits.

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About the Author
Joe Graedon is a pharmacologist who has dedicated his career to making drug information understandable to consumers. His best-selling book, The People’s Pharmacy, was published in 1976 and led to a syndicated newspaper column, syndicated public radio show and web site. In 2006, Long Island University awarded him an honorary doctorate as “one of the country's leading drug experts for the consumer.”.
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